Aircraft airframe noise: Aerodynamics and aeroacoustics of a flap side-edge
Last updated on April 5, 2022
An experimental and computational investigation was carried out to determine the aerodynamics and aeroacoustics of a flap side-edge. A porous side-edge treatment was applied to the flap side-edge in an attempt to reduce airframe noise. The application of a porous flap side-edge had two favourable effects. Firstly, it reduced the magnitude of vorticity in the turbulent shear layer and the vortex. This reduced the magnitude of the hydrodynamic instabilities induced by the flap side-edge vortex. Secondly, it displaced the vortex further away from the flap surface due to the finite mass flux allowed through the porous material. This reduced the magnitude of the disturbances that interacted with the solid flap surface by moving them further away. This research was focused on understanding noise generation mechanisms associated with the flowfield around a flap-side edge and their reduction. Previous investigations identified a noise reduction of up to 4 dB in the far-field, within a limited band of frequencies, by replacing part of a flap side-edge with an open cell porous material. The physics responsible for this were not discussed. This work employed a variety of experimental and numerical techniques to understand the physics responsible for noise production at the flap side-edge and the mechanism by which a porous material applied to the flap side-edge reduced the noise.
